Cardiac and Metabolic Responses to “Space Invaders”: An Instance of Metabolically‐Exaggerated Cardiac Adjustment?

Heart rate, plus various ventilatory and metabolic indices, were monitored while 24 male subjects played a computer game of the “space invaders” type and during a control condition, in which analogous but ineffective actions were requested and the game proceeded automatically. Relative to baseline, subjects showed much larger increases in heart rate during “space invaders” than during the control condition. However, oxygen consumption, carbon dioxide production, respiratory rate and volume also increased more. While the absolute magnitude of metabolic differences between conditions could be regarded as modest relative to heart rate differences, given the effective range of variations possible for each parameter, the existence of highly significant differences in oxygen consumption and carbon dioxide production militates against assertions of overall cardiac‐metabolic independence during “space invaders.” Nevertheless, analysis of individual differences in heart rate reactivity would seem to provide some evidence of metabolically‐unjustified heart rate changes during “space invaders.” High heart rate reactors during “space invaders” did not differ from low reactors in either oxygen consumption or carbon dioxide production. In addition, this relatively high heart rate reactivity was specific to the “space invaders” condition; high and low heart rate reactors displayed no differences in heart rate, or in any other physiological measure, during the control condition or during baseline.